Wow, this is great feedback. Thanks everybody for your input, your giving me much to think about. I guess my main interest in going to the new rubber sole over felt is my concern about invasive species such as "rock snot". I fish mostly in PA, but I do get into different watersheds in various parts of the state and I want to act responsibily in helping minimize the spread of this kind of stuff. My trusty old boots that I want to retire to back up status are felt and have served me well. I have wondered if studs with the felt soles would be an advantage. I am hearing that many of you who have the vibram soles really like them. Thanks again for helping me think this through. Any other thoughts or ideas? Keep the coming!